In farming it is important to monitor the condition of livestock such as beef cattle, dairy cattle, horses, sheep, goats, and swine. Such monitoring provides not only for improving animals' welfare and husbandry but also ensures that the animal is in the best condition for the desired purpose. For beef cattle, for example, it is preferred that the animal has optimum tissue thickening with sufficient marbling to provide the highest quality carcass. In pigs, it is to achieve the desired ratio of lean to fat and determine the target size for slaughter. For dairy cows it is to ensure they are ‘fit not fat’ at pre-calving (drying off) and calving, while they do not have excessive weight loss at early lactation and at service.
Typically, monitoring is achieved by the farmer walking through the herd and determining their condition by sight. To ensure entire herds are seen, the farmer may view each when they are all consecutively weighed, for instance, where he can note the identity number of an animal which gives concern. This process may be sufficient for small herds where one experienced individual has the time to consider each animal. However, the individual's view is very subjective when overall appearance is being considered. Indeed, overall visual appearance can provide little to no information on weight and/or tissue characteristics. As the condition may dictate the expected price at sale, there is a need to provide a more quantitative analysis.
At a first level the sheep and cattle industries have introduced a form of body condition scoring (BCS). In this way, each animal can be graded according to a scale. For dairy cows, in the UK, the scale often used is from one to five with 0.25 point intervals available also. These are primarily based on viewing the animal from the rear, around the tail head, and from the side, along the loin. Table 1 provides the description of scores as determined by the Department for Environment, Food and Rural Affairs (DEFRA) in the UK.
TABLE 1Description of Scores in Dairy CowsCondi-ScoretionDetailed Description1PoorTail Head - deep cavity with no fatty tissue under skin.Skin fairly supple but coat condition often rough.Loin - spine prominent and horizontal processes sharp.2ModerateTail Head - shallow cavity but pin bones prominent;some fat under skin. Skin supple.Loin - horizontal processes can be identifiedindividually with ends rounded.3GoodTail Head - fat cover over whole area and skin smoothbut pelvis can be felt.Loin - end of horizontal process can only be felt withpressure; only slight depression in loin.4FatTail Head - completely filled and folds and patches offat evident.Loin - cannot feel processes and will have completelyrounded appearance.5GrosslyTail Head - buried in fatty tissue, pelvis impalpableFateven with firm pressure.
As can be seen from the descriptions provided, this technique of determination requires both visual and tactile assessment. As a result, it requires a skilled individual to perform it and consequently has major disadvantages in respect of subjectivity and time commitment. In effect, these methods rely upon subjective analysis of physical characteristics of an animal and are, therefore, carried out in an intuitive, rather than scientific manner.
For characteristics that cannot be determined from overall visual appearance and/or human tactile assessment, such as tissue depth and quality, imaging systems have been considered. In particular, for beef cattle, accurate and non-destructive methods of determining back fat and total fat have been developed. Such systems are based on imaging into the tissue using ultrasound. These systems have a number of disadvantages. They are not able to predict the tenderness of meat from a slaughtered animal, either before or after slaughter with any significant degree of accuracy. They require a lubricant to be sprayed or coated on the hide prior to contact by the ultrasound probe for the sound waves to reach the tissue. Also, the animal must remain comparatively still for a period of time. Besides the time taken to record each image, quantitative results are not given in real-time.
Consequently a need has been recognized for an automated measurement and analysis system which can provide a quantitative measurement in terms of a grading for a characteristic in livestock.
Accordingly, digital imaging techniques have been developed for assessing body shape, weight, and fatness of pigs. Simple video camera technology is used to capture the image of the back of the pig as the camera looks down upon the pig. Using mathematical algorithms, the outline of the body can be traced and the enclosed area determined. This area measurement has been found to correlate with the weigh platform weight for different breed types. While weight is a good condition indicator for pigs it is of more limited use in cattle where the body part and body composition is of greater consequence on condition.
Digital images of dairy cows have been recorded by taking a visual image of the rear of the animal. Such images are then assessed by an experienced individual who provides graded scores (BCS) in much the same way as if the individual viewed the animal directly. While such a method allows farms on which an experienced individual is not present to acquire the scores, the method suffers from even greater subjectivity problems as only a portion of the cow is viewed and there is no opportunity for tactile assessment.
Attempts to provide an automated system have produced laser scanning devices which model contours or curvatures taken from the rear of the animal at the tail, head and buttocks. These systems have had limited success due to the inherent difficulties in positioning the cow relative to a laser system directed towards its rear in a farm environment. Any movement during image collection also creates errors in the dimensional information collected. As a result poor quality images are typically obtained and some have been found to bear little relevance to the animal when viewed, even though the scoring may have been similar. This may be a result of the fact that the protrusion of bones in a cow, the common markers considered in imaging, may not necessarily mean that she is thin.